Severe feed restriction in pullets during the early growing period: performance and relationships among age, body weight, and egg weight at the onset of production.

The performance of egg type (Leghorn x Rhode Island Red) chickens that were feed restricted during the prelaying period was studied in two trials, each conducted with 300 hens. In Trial 1, treatments included 1) an ad libitum-fed control; 2) restriction for close to zero growth between 7 and 28 days of age; 3) the same restriction as (2) but continued by restriction of 50% growth up to 70 days; 4) restriction between 7 and 70 days for 50% growth; and 5) restriction for 50% growth between 7 and 98 days. In Trial 2, birds were restricted severely (close to zero growth) from 7 to 28 days of age, followed by restriction of 50% growth up to 28, 56, 84, and 112 days of age, respectively. In all cases, feed restriction resulted in a delay in the onset of egg production, leading to some increases in egg weight. Egg production rate and cumulative production were not affected, in most cases, by early feed restriction. The BW at the onset and after 20 mo of production was reduced when feed restriction was continued beyond the age of 84 days. Overall feed conversion (grams feed per egg) and feed efficiency (grams feed per gram egg mass) were not affected significantly by feed restriction, although feed efficiency (grams gain per gram feed) was improved during the prelaying period. Within each treatment, BW was positively correlated with age at onset of egg production. Egg weight was a function of both age and BW at the onset of production. The significant correlation between egg weight and BW was maintained even after a year of production.